Cooling System Help

[tnt31]

2007 Saturn Relay w/3.9L w/125K miles. (Same as Chevy Uplander and Buick Terezza) Wife's vehicle. I think this GM 3.9L is/has been used in several different vehicles.

About 8 months ago vehicle started running hot on occasion. Took it to a local mechanic who changed the thermostat. It was better for a few months but then started acting as if overheated although had no symptoms of being hot other than temp gauge pegged and a message of being in overheat protection AC Shut off and it puts both fans in high speed. After some research determined a bad Coolant Temp Sensor would cause those symptoms. Mechanic changed that about 3 months ago and all has been well since until about 2 weeks ago. Wife complained it was doing some of the same as previously described about running hot but no symptoms of it actually being hot. (However that may be an incorrect assesment) I checked it a few times and all looked OK. However she mentioned it happened again Friday so yesterday I take a look at it and for the first time it is low on coolant. The overflow tank is empty and it takes maybe a quart (maybe a little less) to fill up the coolant once I removed the cap and then I fill up the overflow. I decided to try to make sure no bubble(s) in the system so I hook up the lisle spill proof funnel and fill it about a fourth to third full. I start up the vehicle and see a few small bubbles coming up but nothing abnormal. After about 8 to 10 minutes of running the coolant violently bubbles and explodes out the funnel. I shut it off, clean up the mess, let it cool down a bit and try again. I get the same result. I have not used this funnel a whole lot but the few times I have I never got this kind of result.

Any idea what would/could cause this?

Thanks

 

[Trav]

Typical head gasket symptoms unless it has a a large amount of air trapped in the system.
Bleed the system and try it again if it still does it time to investigate further.

 

[doitmyself]

Could a bad water pump cause these symptoms?

 

[JimPghPA]

The eruption of bubbles could simply be that the coolant had gotten hot enough to boil at atmospheric pressure, or it could mean a leak of exhaust into the cooling system via a bad gasket. The fact that you had to run it for awhile before it erupted means it probably was just that the coolant was hot enough to boil at atmospheric pressure.

If it was a bad gasket it probably would erupt even if the engine was stone cold from sitting overnight and you just started it up.

 

[mk378]

Sounds like boiling inside the engine. Remove thermostat and test in hot water, or just replace. Water pumps that turn but don't pump are very rare. That only happens when there is severe corrosion from using plain water or worn-out coolant.

 

[Nick1994]

Replace the thermostat with an OEM one, not some cheap Chinese aftermarket like a Stant.

But it does sound a bit like a head gasket issue.

 

[andyd]

Originally Posted By: mk378
Sounds like boiling inside the engine. Remove thermostat and test in hot water, or just replace. Water pumps that turn but don't pump are very rare. That only happens when there is severe corrosion from using plain water or worn-out coolant.
It does happen. The impeller separates from the shaft

 

[Trav]

As other have posted check everything first then look into TSB #4196, its a HG TSB for these engines, there is another for cooling crossover pipe leak.

 

[Kuato]

Seen this in multiple vehicles - your 10-year-old radiator could have enough scaling inside to degrade the cooling ability. Might be time for a new rad.

 

[CR94]

Originally Posted By: andyd
Originally Posted By: mk378
... Water pumps that turn but don't pump are very rare. ...
It does happen. The impeller separates from the shaft
Yes. That happened with the original water pump of my sister's Dodge Omni, circa 1979.